Since it not only helps your child trust you more it also establishes a companionship between you all. It is really healthy for your child if they can let go and have fun with you. As a matter of fact, sometimes you learn new things about your child.
Play time with your child is also your chance to teach your child values that are going to be with them for their whole lives. In fact through this you can also learn about how your childhood interacts with the outside world, pretty early on. Apart from all of it being beneficial for your child. Playing with your own child also keeps your own inner child active. It helps you connect to those parts of your personality that only existed when you were very young.